This invention relates to a rear projection type display of a large screen (for example, about 1.5 m to about 3 m in width), and particularly to the construction of a transmission-type screen therefor.
U.S. Pat. No. 4,536,056 "Rear Projection Apparatus" filed by this inventor discloses the construction of a transmission type screen lenticular lens suitable for the projection type display using a plurality of CRTs for projection. In this gazette, it is described that the elements constituting the screen may be either one of the circular Fresnel lens and the linear Fresnel lens.
In addition, U.S. Pat. No. 4,725,134 "Rear Projection Apparatus" filed by this inventor discloses means for preventing the moire interference from occurring between the exiting surface type circular Fresnel lens and the lenticular lens.
At the present time, the screen based on the principle of both the gazettes given above has already been massproduced and contributed to the business world. However, the size of the screen is limited to about 1.4 m in the maximum width and about 1.1 m in height. This limitation is ascribed to the fact that the lenticular lens is produced on the basis of the extrusion roll molding process and that the effective lateral width of the extrusion roll molding machine is limited to about 1.4 m.
Moreover, the circular Fresnel lens, which is produced by casting molding or press molding, is difficult to produce with 1.4 m or above in width and with high performance.
Also, in the cross lenticular type screen without use of the Fresnel lens, a large number of lenticular lenses of about 1.2 m in width are joined together by bonding technique to produce a lens of 2 m or above in width which is practically used. However, the use of this cross lenticular type screen is limited to the projection system of a large projection distance (exactly speaking, projection distance/lateral width ratio) since it has no Fresnel lens element. Therefore, it is difficult to construct the projection type display of a short projection distance, or a small depth.
The transmission type screen using the liner Fresnel lens has not been put into practical use yet (at least, this inventor does not know any example of that screen).